In the related art, an inspection method (also known as a biopsy) that samples a small amount of a body tissue and observes the tissue with a microscope is known. When a tissue of a deep part of internal organs or the like, is sampled, observation using an optical endoscope is difficult. Therefore, an ultrasonic tomogram for the internal organs by an ultrasonic endoscope or the like may be acquired, and a biopsy needle may be inserted into the internal organs under ultrasonic observation to sample a tissue. A treatment tool for the biopsy to be used for such an application is described in Japanese Unexamined Patent Application, First Publication No. 3890013 (referred to herein as “Patent Document 1”). If a distal end of the treatment tool includes a tubular needle tube that is sharply formed, and the needle tube is inserted into a tissue, a portion of the tissue enters the inside of the needle tube. By extracting the needle tube, the tissue that has entered the inside of the needle tube can be sampled.